Energy-saving compression valve of the rock drill

The relevance of the research is due to the necessity to create pneumatic rock drills with low air consumption. The article analyzes the reasons for low efficiency of percussive machines. The authors state that applying a single distribution body in the percussive mechanism does not allow carrying out a low-energy operating cycle of the mechanism. Using the studied device as an example, it is substantiated that applying a compression valve with two distribution bodies separately operating the working chambers makes it possible to significantly reduce the airflow. The authors describe the construction of a core drill percussive mechanism and the operation of a compression valve. It is shown that in the new percussive mechanism working chambers are cut off the circuit by the time when exhaust windows are opened by the piston and air is not supplied into the cylinder up to 20% of the cycle time. The air flow rate of the new mechanism was 3.8 m3/min. In comparison with the drill PK-75, the overall noise level of the new machine is lower by 8-10 dB, while the percussive mechanism efficiency is 2.3 times higher

Shock-induced reaction in several liquids

Single-shock experiments have been completed in several liquids using multiple, embedded, electromagnetic Lagrangian particle velocity and impulse gauges to measure shock waveforms. The liquids include acrylonitrile, bromoform, diiodomethane, phenylacetylene, bromocyclopropane, and carbon disulfide. Some of these are known to exhibit shock-induced reaction and others are considered to be candidates for reaction studies. The ''universal'' liquid Hugoniot, which depends only on initial condition sound speed, was used to calculate the unreacted Hugoniot. Sound velocities were measured for those liquids with no data available. The effects of shock-induced reaction are clearly identified in the particle velocity waveforms for some materials, but there are remaining questions about whether reactions occur in others. The most impressive results are that the full reactive, two-wave structure was measured in phenylacetylene. On the reacting materials with two-wave structures, the particle velocity waveforms had a decrease behind the top of the first wave. This is thought to be evidence of an early reaction which occurs at the top of the first (nonreactive) wave. 12 refs., 2 figs., 1 tab

Impact of adherence on growth response during the first 2 years of growth hormone treatment

Purpose Adherence to growth hormone (GH) treatment impacts clinical outcomes. The aim of this study is to assess the impact of adherence to rhGH treatment (2 years) on auxological outcomes. Methods Multicentric, retrospective observational study in rhGH-naive GHD/SGA children treated with Saizen (R) during >= 2 years. Growth response was assessed by evaluating the change in height standard deviation score (Delta H SDS) and the index of responsiveness (IoR). Adherence was monitored using EasyPod (TM) Connect device. Results A total of 110 patients (3 Spanish centers) were evaluable (GHD n = 76, SGA n = 34). Adherence was 95.6 and 93.9% (year 1, 2). SGA and GHD children showed an increase of 0.6 cm/year and 1.1 cm/year for each 10% adherence modification. Lower adherence was observed in patients with lower pretreatment height velocity (HV) and in patients whose parents had a lower level of education. A positive correlation between index of responsiveness (IoR) during the first and second years with HV SDS during the second year and between IoR2 and adherence (year 1, 2) was observed. The frequency of patients with HV > 1 SD was higher (p = 0.025) among patients with adherence >90%. The best model to predict the height gain(cm) reaching an adjusted R squared of 0.489 involved percentage of adherence, Tanner stage, pretreatment HV, dose of rhGH, and whether the treatment was initiated before or after puberty. Conclusions Adherence during the first 2 years of response was very high >90% and showed a negative association with age, pretreatment HV and treatment duration and a positive correlation with the level of parent education

Progress in measuring detonation wave profiles in PBX9501

The authors have measured detonation wave profiles in PBX9501 (95 wt% HMX and 5 wt% binders) using VISAR. Planar detonations were produced by impacting the explosive with projectiles launched in a 72 mm bore gas gun. Particle velocity wave profiles were measured at the explosive/window interface using two VISARs with different fringe constants. Windows with very thin vapor deposited aluminum mirrors were used for all experiments. PMMA windows provided an undermatch, and LiF (Lithium Fluoride) windows provided an overmatch to the explosive, reacted and unreacted. While the present experiments do not have adequate time resolution to adequately resolve the ZND spike condition, they do constrain it to lie between 38.7 and 53.4 Gpa or 2.4 and 3.3 km/s. Accurate knowledge of the CJ state places the reaction zone length at 35 {+-} 12 ns ({approx} 0.3 mm). The present experiments do not show any effect of the window on the reaction zone; both window materials result in the same reaction zone length

Detonation wave profiles in HMX based explosives

Detonation wave profiles have been measured in several HMX based plastic bonded explosives including PBX9404, PBX9501, and EDC-37, as well as two HMX powders (coarse and fine) pressed to 65% of crystal density. The powders had 120 and 10 {micro}m average grain sizes, respectively. Planar detonations were produced by impacting the explosive with projectiles launched in a 72-mm bore gas gun. Impactors, impact velocity, and explosive thickness were chosen so that the run distance to detonation was always less than half the explosive thickness. For the high density plastic bonded explosives, particle velocity wave profiles were measured at an explosive/window interface using two VISAR interferometers. PMMA windows with vapor deposited aluminum mirrors were used for all experiments. Wave profiles for the powdered explosives were measured using magnetic particle velocity gauges. Estimates of the reaction zone parameters were obtained from the profiles using Hugoniots of the explosive and window

Long-distance soliton transmission through ultralong fiber lasers

We present the first experimental demonstration (to our knowledge) of long-distance unperturbed fundamental optical soliton transmission in conventional single-mode optical fiber. The virtual transparency in the fiber required for soliton transmission, over 15 complete periods, was achieved by using an ultralong Raman fiber laser amplification scheme. Optical soliton pulse duration, pulse bandwidth, and peak intensity are shown to remain constant along the transmission length. Frequency-resolved optical gating spectrograms and numerical simulations confirm the observed optical soliton dynamics

Observations of shock-induced reaction in liquid bromoform up to 11 GPA

Shock measurements on bromoform (CHBr{sub 3}) over the past 33 years at Los Alamos have led to speculation that this material undergoes a shock-induced reaction. Ramsay observed that it became opaque after a 1 to 2 {micro}s induction time when shocked to pressures above 6 GPa. McQueen and Isaak observed that it is a strong light emitter above 25 GPa. Hugoniot data start to deviate from the anticipated liquid Hugoniot at pressures above 10 GPa. The authors have used electromagnetic particle velocity gauging to measure wave profiles in shocked liquid bromoform. At pressures below 9 GPa, there is no mechanical evidence of reaction. At a pressure slightly above 10 GPa, the observed wave profiles are similar to those observed in initiating liquid explosives such as nitromethane. Their characteristics are completely different from the two-wave structures observed in shocked liquids where the products are more dense than the reactants. As with explosives, a reaction producing products which are less dense than the reactants is indicated. BKW calculations also indicate that a detonation type reaction may be possible

Changes to the LANL gas-driven two-stage gun: Magnetic gauge instrumentation, etc.

Our gas-driven two-stage gun was designed and built to do initiation studies on insensitive high explosives as well as other equation of state experiments on inert materials. Our preferred method of measuring initiation phenomena involves the use of magnetic particle velocity gauges. In order to accommodate this type of gauging in our two-stage gun, projectile velocity was sacrificed in favor of a larger experimental target area (obtained by using a 50 mm diameter launch tube). We have used magnetic gauging on our 72-mm bore diameter single-stage gun for over 15 years and it has proven a very effective technique to monitor reactive shock wave evolution. This technique has now been adapted to our gas-driven two-stage gun. We describe the method used, as well as some of the difficulties that arose while installing this technique. Several magnetic gauge experiments have been completed on plastic materials. Waveforms obtained in one experiment are given, along with the Hugoniot information that was obtained. This new technique is now working quite well, as is evidenced by the data. To our knowledge, this is the first time magnetic gauging has been used on a two-stage gun. We have also made changes to the burst diaphragm package in the transition section to ensure that the petals do not break off during the opening process and to increase the burst pressure. This will also be discussed briefly